US20240167423A1 - Airfoil last chance screen utilizing edm and afm - Google Patents
Airfoil last chance screen utilizing edm and afm Download PDFInfo
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- US20240167423A1 US20240167423A1 US17/990,343 US202217990343A US2024167423A1 US 20240167423 A1 US20240167423 A1 US 20240167423A1 US 202217990343 A US202217990343 A US 202217990343A US 2024167423 A1 US2024167423 A1 US 2024167423A1
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- 239000002184 metal Substances 0.000 claims abstract description 56
- 238000009760 electrical discharge machining Methods 0.000 claims abstract description 46
- 238000007493 shaping process Methods 0.000 claims abstract description 22
- 238000004519 manufacturing process Methods 0.000 claims abstract description 11
- 238000000034 method Methods 0.000 claims description 61
- 229910045601 alloy Inorganic materials 0.000 claims description 5
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- 239000010935 stainless steel Substances 0.000 claims description 3
- 239000000446 fuel Substances 0.000 description 102
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- 239000002828 fuel tank Substances 0.000 description 10
- 238000003754 machining Methods 0.000 description 9
- 238000004939 coking Methods 0.000 description 7
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- 239000007921 spray Substances 0.000 description 2
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- 239000004677 Nylon Substances 0.000 description 1
- 229910000831 Steel Inorganic materials 0.000 description 1
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- 229910000601 superalloy Inorganic materials 0.000 description 1
Images
Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02C—GAS-TURBINE PLANTS; AIR INTAKES FOR JET-PROPULSION PLANTS; CONTROLLING FUEL SUPPLY IN AIR-BREATHING JET-PROPULSION PLANTS
- F02C7/00—Features, components parts, details or accessories, not provided for in, or of interest apart form groups F02C1/00 - F02C6/00; Air intakes for jet-propulsion plants
- F02C7/22—Fuel supply systems
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23P—METAL-WORKING NOT OTHERWISE PROVIDED FOR; COMBINED OPERATIONS; UNIVERSAL MACHINE TOOLS
- B23P15/00—Making specific metal objects by operations not covered by a single other subclass or a group in this subclass
- B23P15/16—Making specific metal objects by operations not covered by a single other subclass or a group in this subclass plates with holes of very small diameter, e.g. for spinning or burner nozzles
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D39/00—Filtering material for liquid or gaseous fluids
- B01D39/10—Filter screens essentially made of metal
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23H—WORKING OF METAL BY THE ACTION OF A HIGH CONCENTRATION OF ELECTRIC CURRENT ON A WORKPIECE USING AN ELECTRODE WHICH TAKES THE PLACE OF A TOOL; SUCH WORKING COMBINED WITH OTHER FORMS OF WORKING OF METAL
- B23H7/00—Processes or apparatus applicable to both electrical discharge machining and electrochemical machining
- B23H7/02—Wire-cutting
- B23H7/08—Wire electrodes
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23H—WORKING OF METAL BY THE ACTION OF A HIGH CONCENTRATION OF ELECTRIC CURRENT ON A WORKPIECE USING AN ELECTRODE WHICH TAKES THE PLACE OF A TOOL; SUCH WORKING COMBINED WITH OTHER FORMS OF WORKING OF METAL
- B23H9/00—Machining specially adapted for treating particular metal objects or for obtaining special effects or results on metal objects
- B23H9/14—Making holes
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B24—GRINDING; POLISHING
- B24C—ABRASIVE OR RELATED BLASTING WITH PARTICULATE MATERIAL
- B24C3/00—Abrasive blasting machines or devices; Plants
- B24C3/32—Abrasive blasting machines or devices; Plants designed for abrasive blasting of particular work, e.g. the internal surfaces of cylinder blocks
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B24—GRINDING; POLISHING
- B24C—ABRASIVE OR RELATED BLASTING WITH PARTICULATE MATERIAL
- B24C3/00—Abrasive blasting machines or devices; Plants
- B24C3/32—Abrasive blasting machines or devices; Plants designed for abrasive blasting of particular work, e.g. the internal surfaces of cylinder blocks
- B24C3/325—Abrasive blasting machines or devices; Plants designed for abrasive blasting of particular work, e.g. the internal surfaces of cylinder blocks for internal surfaces, e.g. of tubes
- B24C3/327—Abrasive blasting machines or devices; Plants designed for abrasive blasting of particular work, e.g. the internal surfaces of cylinder blocks for internal surfaces, e.g. of tubes by an axially-moving flow of abrasive particles without passing a blast gun, impeller or the like along the internal surface
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2201/00—Details relating to filtering apparatus
- B01D2201/18—Filters characterised by the openings or pores
- B01D2201/184—Special form, dimension of the openings, pores of the filtering elements
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23H—WORKING OF METAL BY THE ACTION OF A HIGH CONCENTRATION OF ELECTRIC CURRENT ON A WORKPIECE USING AN ELECTRODE WHICH TAKES THE PLACE OF A TOOL; SUCH WORKING COMBINED WITH OTHER FORMS OF WORKING OF METAL
- B23H1/00—Electrical discharge machining, i.e. removing metal with a series of rapidly recurring electrical discharges between an electrode and a workpiece in the presence of a fluid dielectric
- B23H1/04—Electrodes specially adapted therefor or their manufacture
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23H—WORKING OF METAL BY THE ACTION OF A HIGH CONCENTRATION OF ELECTRIC CURRENT ON A WORKPIECE USING AN ELECTRODE WHICH TAKES THE PLACE OF A TOOL; SUCH WORKING COMBINED WITH OTHER FORMS OF WORKING OF METAL
- B23H7/00—Processes or apparatus applicable to both electrical discharge machining and electrochemical machining
- B23H7/02—Wire-cutting
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23H—WORKING OF METAL BY THE ACTION OF A HIGH CONCENTRATION OF ELECTRIC CURRENT ON A WORKPIECE USING AN ELECTRODE WHICH TAKES THE PLACE OF A TOOL; SUCH WORKING COMBINED WITH OTHER FORMS OF WORKING OF METAL
- B23H9/00—Machining specially adapted for treating particular metal objects or for obtaining special effects or results on metal objects
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23P—METAL-WORKING NOT OTHERWISE PROVIDED FOR; COMBINED OPERATIONS; UNIVERSAL MACHINE TOOLS
- B23P2700/00—Indexing scheme relating to the articles being treated, e.g. manufactured, repaired, assembled, connected or other operations covered in the subgroups
- B23P2700/13—Parts of turbine combustion chambers
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
- F05D—INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
- F05D2220/00—Application
- F05D2220/30—Application in turbines
- F05D2220/32—Application in turbines in gas turbines
- F05D2220/323—Application in turbines in gas turbines for aircraft propulsion, e.g. jet engines
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
- F05D—INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
- F05D2230/00—Manufacture
- F05D2230/10—Manufacture by removing material
- F05D2230/12—Manufacture by removing material by spark erosion methods
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
- F05D—INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
- F05D2260/00—Function
- F05D2260/60—Fluid transfer
- F05D2260/607—Preventing clogging or obstruction of flow paths by dirt, dust, or foreign particles
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- General Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Electrical Discharge Machining, Electrochemical Machining, And Combined Machining (AREA)
Abstract
A method of manufacturing a last chance screen for an aircraft engine includes forming an array of holes through a metal sheet with a wire electrode using electrical discharge machining. The array of holes comprises a plurality of holes. Each hole of the plurality of holes comprises a first end and a second end and is surrounded by a wall section such that the last chance screen is defined by the plurality of holes and the plurality of wall sections. The first and second end of each hole are widened by either applying a flow of an abrasive flow medium to the array of holes in two directions or using a conical sinker electrode on either side of the metal sheet. Shaping the first and second end of each hole results in an airfoil-shaped cross-section of each wall section.
Description
- The present application relates generally to aircraft fuel systems and in particular to methods of manufacturing last chance screens for aircraft fuel systems.
- Fuel systems are included in aircraft to provide fuel to combustors of gas turbine aircraft engines, and can include fuel tanks and fuel processing systems that are configured to condition and meter the fuel flow to the combustor of the aircraft engines. A last chance screen can be positioned in a fuel conduit extending from the fuel tank and fuel processing system to the aircraft engine. Last chance screens are designed to filter particles out of fuel to prevent particles from flowing into the aircraft engine and clogging components in the aircraft engine such as fuel nozzles configured to spray the fuel into the combustor. The fuel flows through openings in the screen that are sized to filter particles out of the fuel. However, conventional last chance screens formed of woven wire mesh are highly susceptible to coking, where insoluble deposits accumulate on the surfaces of the last chance screens and cause clogging of the last chance screen. Clogging of this kind creates or increases a pressure drop across the last chance screens, which can impact the efficiency of the aircraft engine positioned downstream of the last chance screen. Further, the deposits that accumulate on the surface of the last chance screens can shear or break off and be carried downstream into the aircraft engine, causing clogging of engine components such as the fuel nozzles. As the temperature of fuel flowing through a last chance screen increases, the last chance screen becomes more susceptible to coking.
- Last chance screens with holes having a wider end than a central point (resulting in the wall sections separating the holes having an airfoil-shaped cross-section) outperform conventional woven mesh screens by reducing the surfaces that are normal to the fuel flow through the screen. This reduction in flow-orthogonal surface area helps to reduce coking on the last chance screen. However, the tapered shape of such wall sections is difficult to achieve using traditional screen making techniques, such as stamping or electrical discharge machining hole drilling processes.
- According to one aspect of the present invention, a method of manufacturing a last chance screen for an aircraft engine includes forming an array of holes through a metal sheet with a wire electrode using electrical discharge machining. The array of holes comprises a plurality of holes. Each hole of the plurality of holes extends from a first end to a second end. Each hole is surrounded by a wall section such that the last chance screen is defined by the plurality of holes and the plurality of wall sections. The first end of each hole is shaped by applying a flow of an abrasive flow medium to the array of holes in a first direction, such that the first end of each hole is widened by the flow of the abrasive flow medium and a portion of the wall section adjacent to the first end of each hole has a first convex curvature with respect to the hole. The second end of each hole is shaped by applying a flow of the abrasive flow medium to the array of holes in a second direction which is opposite to the first direction, such that the second end of each hole is widened by the flow of the abrasive flow medium and a portion of the wall section adjacent to the second end of each hole has a second convex curvature with respect to the hole. Shaping the first end of each hole and shaping the second end of each hole results in an airfoil-shaped cross-section of each wall section.
- According to another aspect of the present invention, a method of manufacturing a last chance screen for an aircraft engine includes forming an array of holes through a metal sheet with a wire electrode using electrical discharge machining. The array of holes comprises a plurality of holes. Each hole of the plurality of holes extends from a first end to a second end. Each hole is surrounded by a wall section such that the last chance screen is defined by the plurality of holes and the plurality of wall sections. The first end of each hole is shaped with a first conical sinker electrode using electrical discharge machining, such that the first end of each hole is widened by the electrical discharge machining and a portion of the wall section adjacent to the first end of each hole has a first convex curvature with respect to the hole. The second end of each hole is shaped with a second conical sinker electrode using electrical discharge machining, such that the second end of each hole is widened by the electrical discharge machining and a portion of the wall section adjacent to the second end of each hole has a second convex curvature with respect to the hole. Shaping the first end of each hole and shaping the second end of each hole results in an airfoil-shaped cross-section of each wall section.
- The present summary is provided only by way of example, and not limitation. Other aspects of the present disclosure will be appreciated in view of the entirety of the present disclosure, including the entire text, claims, and accompanying figures.
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FIG. 1 is a schematic depiction of a fuel system for an aircraft engine. -
FIG. 2A is a top plan view of a last chance screen. -
FIG. 2B is a cross-sectional side view of airfoil-shaped wall sections within the last chance screen ofFIG. 2A . -
FIG. 3 depicts a method of creating airfoil-shaped wall sections in a last chance screen. -
FIG. 4A is a cross-sectional side view of a metal sheet. -
FIG. 4B is a cross-sectional side view of the metal sheet ofFIG. 4A after holes have been formed in the sheet by a wire electrode using EDM. -
FIG. 4C is a cross-sectional side view of the metal sheet ofFIG. 4B after the holes have been shaped by AFM in a first direction. -
FIG. 4D is a cross-sectional side view of the metal sheet ofFIG. 4C after the holes have been shaped by AFM in a second direction which is opposite to the first direction. -
FIG. 5 depicts a method of creating airfoil-shaped holes in a last chance screen using shaped EDM electrodes. -
FIG. 6A is a cross-sectional side view of a metal sheet. -
FIG. 6B is a cross-sectional side view of the metal sheet ofFIG. 6A after holes have been formed in the sheet by a wire electrode using EDM. -
FIG. 6C is a cross-sectional side view of the metal sheet ofFIG. 6B after a first end of each hole has been shaped by a first conical sinker electrode using EDM. -
FIG. 6D is a cross-sectional side view of the metal sheet ofFIG. 6C after a second end of each hole has been shaped by a second conical sinker electrode using EDM. -
FIG. 7A is a top plan view of a last chance screen with a square hole grid. -
FIG. 7B is a top plan view of a last chance screen with a hexagonal hole grid. - While the above-identified figures set forth one or more embodiments of the present disclosure, other embodiments are also contemplated, as noted in the discussion. In all cases, this disclosure presents the invention by way of representation and not limitation. It should be understood that numerous other modifications and embodiments can be devised by those skilled in the art, which fall within the scope and spirit of the principles of the invention. The figures may not be drawn to scale, and applications and embodiments of the present invention may include features and components not specifically shown in the drawings.
- A last chance screen having tapered holes surrounded by airfoil-shaped wall sections can reduce deposits on the screen by reducing the number of surfaces that are normal to the fuel flow. Electrical discharge machining (EDM) can be used to partially or fully shape these airfoil-shaped wall sections within the screen. Abrasive flow machining (AFM) can be combined with EDM processes to further shape the airfoil-shaped wall sections.
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FIG. 1 is a schematic depiction offuel system 10 foraircraft engine 12.FIG. 1 showsfuel system 10 andaircraft engine 12.Fuel system 10 includesfuel tank 14,fuel processing system 16, andlast chance screen 18.Aircraft engine 12 includesfuel nozzle 20 andcombustor 22. -
Fuel system 10 is configured to store, condition, and deliver fuel toaircraft engine 12.Fuel system 10 includesfuel tank 14 that stores fuel for use inaircraft engine 12.Fuel tank 14 can be positioned in any suitable location on an aircraft.Fuel tank 14 is fluidly coupled tofuel processing system 16 using a fuel conduit. Fuel flows fromfuel tank 14 tofuel processing system 16, which is configured to condition and meter the fuel flow. Conditioning the fuel can include adjusting the pressure and temperature of the fuel and filtering the fuel.Last chance screen 18 is positioned in a fuel conduit extending betweenfuel processing system 16 andaircraft engine 12 and is fluidly coupled tofuel tank 14 andfuel processing system 16 that are upstream oflast chance screen 18.Last chance screen 18 is designed to filter a fuel flow immediately before the fuel flow entersaircraft engine 12, and can thereby remove particles from the fuel to prevent these particles from flowing intoaircraft engine 12 and clogging components withinaircraft engine 12, such as fuel nozzle(s) 20. The location oflast chance screen 18 withinfuel system 10 allowslast chance screen 18 to filter out particles that are introduced into the fuel flow during operation offuel system 10, such as debris from machining processes or wear. -
Aircraft engine 12 includesfuel nozzle 20 andcombustor 22.Fuel nozzle 20 andcombustor 22 are fluidly coupled tofuel system 10, includingfuel tank 14,fuel processing system 16, andlast chance screen 18. Fuel flows fromfuel processing system 16 throughlast chance screen 18 to fuelnozzle 20, which sprays the fuel intocombustor 22 for use byaircraft engine 12. Onelast chance screen 18 and onefuel nozzle 20 are shown inFIG. 1 , but any suitable number of last chance screens 18 andfuel nozzles 20 can be included in alternate embodiments. At least onelast chance screen 18 will be positioned in each fuel conduit leading to onefuel nozzle 20. In alternate embodiments, two or more last chance screens 18 can be positioned in each fuel conduit leading to onefuel nozzle 20. Further, last chance screens can be positioned betweenfuel tank 14 andfuel processing system 16 in some embodiments. -
Fuel nozzle 20 has small and intricate passages and orifices that are designed to obtain the desired degree of fuel distribution and atomization incombustor 22. Debris and contaminant particles can be generated infuel system 10.Last chance screen 18 is designed to filter the debris and contaminant particles out of the fuel prior to the fuel being delivered tofuel nozzle 20. This will prevent the debris and contaminant particles from clogging the passages and orifices offuel nozzle 20. -
FIG. 2A is a top plan view oflast chance screen 100.FIG. 2B is a cross-sectional view oflast chance screen 100 taken along line 2B-2B ofFIG. 2A .Last chance screen 100 includesupstream end 102, downstream end 104 (shown inFIG. 2B ), andmesh 106, which includesfirst members 108,second members 110, andopenings 112. Each member offirst members 108 andsecond members 110 haveleading edge 120, trailing edge 122 (shown inFIG. 2B ),first side 124, andsecond side 126.First side 124 includes firstoutermost edge 130, first leading contouredsurface 132, and first trailing contouredsurface 134.Second side 126 includes secondoutermost edge 140, second leading contouredsurface 142, and second trailing contouredsurface 144.FIG. 2B shows flow arrows F and width W. -
Last chance screen 100 is a last chance screen according to the present disclosure that can be used in fuel system 10 (shown inFIG. 1 ).Last chance screen 100 hasupstream end 102 anddownstream end 104 opposite ofupstream end 102.Last chance screen 100 is configured to be positioned in a fuel conduit betweenfuel processing system 16 and fuel nozzle 20 (both shown inFIG. 1 ). In some examples,last chance screen 100 has a diameter of approximately 0.250 inches.Upstream end 102 is configured to facefuel processing system 16, anddownstream end 104 is configured to facefuel nozzle 20.Last chance screen 100 is configured to be positioned in the fuel conduit to filter the fuel flowing fromfuel process system 22 tofuel nozzle 20. Fuel will flow throughupstream end 102 and then out ofdownstream end 104 oflast chance screen 100. -
Last chance screen 10 includesmesh 106 havingfirst members 108 running in a first direction andsecond members 110 running in a second direction and intersectingfirst members 108. In the embodiment shown inFIGS. 2A-2B , the second direction is perpendicular to the first direction.First members 108 andsecond members 110 intersect one another to formmesh 106, as shown inFIG. 2A .First members 108 andsecond members 110 have airfoil-shaped cross-sections.Openings 112 are formed inmesh 106 betweenfirst members 108 andsecond members 110. As shown inFIGS. 2A-2B ,openings 112 are square shaped. In alternate embodiments,openings 112 can be circular, rectangular, elliptical, or any other suitable shape. In some examples,mesh 106 withinlast chance screen 100 can have a diameter of approximately 0.18 inches. - As shown in
FIG. 2B ,first members 108 andsecond members 110 have airfoil-shaped cross-sections. Each member offirst members 108 andsecond members 110 haveleading edge 120 atupstream end 102 oflast chance screen 100 and trailingedge 122 atdownstream end 104 oflast chance screen 100.First side 124 extends from leadingedge 120 to trailingedge 122, andsecond side 126 is opposite offirst side 124 and extends from leadingedge 120 to trailingedge 122.First side 124 has firstoutermost edge 130 betweenleading edge 120 and trailingedge 122 that is the outermost edge offirst side 124 ofsecond member 110. First leading contouredsurface 132 extends betweenleading edge 120 and firstoutermost edge 130 onfirst side 124, and first trailing contouredsurface 134 extends between firstoutermost edge 130 and trailingedge 122 onfirst side 124. Firstoutermost edge 130 is positioned downstream of a central axis of each member offirst members 108 andsecond members 110. First leading contouredsurface 132 has a greater length than first trailing contouredsurface 134 in the embodiment shown inFIGS. 2A-2B . In alternate embodiments, first leading contouredsurface 132 and first trailing contouredsurface 134 can be the same length or first trailing contouredsurface 134 can have a greater length than first leading contouredsurface 132.Second side 126 has secondoutermost edge 140 betweenleading edge 120 and trailingedge 122 that is the outermost edge ofsecond side 126 ofsecond member 110. Second leading contouredsurface 142 extends betweenleading edge 120 and secondoutermost edge 140 onsecond side 126, and second trailing contouredsurface 144 extends between secondoutermost edge 140 and trailingedge 122 onsecond side 126. Secondoutermost edge 140 is positioned downstream of a central axis of each member offirst members 108 andsecond members 110. Second leading contouredsurface 142 has a greater length than second trailing contouredsurface 144 in the embodiment shown inFIGS. 2A-2B . In alternate embodiments, second leading contouredsurface 142 and second trailing contouredsurface 144 can be the same length or second trailing contouredsurface 144 can have a greater length than second leading contouredsurface 142. - The airfoil-shaped cross-section of
first members 108 andsecond members 110 is a biconvex shaped cross-section. Leadingedge 120 forms an upstream tip of the airfoil-shaped cross-section, and trailingedge 122 forms a downstream tip of the airfoil-shaped cross-section.First side 124 andsecond side 126 both bulge outwards to form convex shaped sides of the airfoil-shaped cross-section. - The airfoil-shaped cross-section of
first members 108 andsecond members 110 creates converging nozzles and diverging nozzles onlast chance screen 100. Eachopening 112 ofmesh 106 oflast chance screen 100 is surrounded by twofirst members 108 and twosecond members 110.First side 124 of onefirst member 108,second side 126 of an adjacentfirst member 108,first side 124 of onesecond member 110, andsecond side 126 of an adjacentsecond member 110 surround eachopening 112 inmesh 106 oflast chance screen 100. First leading contouredsurface 132 of the onefirst member 108, second leading contouredsurface 142 of the adjacentfirst member 108, first leading contouredsurface 132 of the onesecond member 110, and second leading contouredsurface 142 of the adjacentsecond member 110 form a converging nozzle leading to the narrowest portion ofopening 112. First trailing contouredsurface 134 of the onefirst member 108, second trailing contouredsurface 144 of the adjacentfirst member 108, first trailing contouredsurface 134 of the onesecond member 110, and second trailing contouredsurface 144 of the adjacentsecond member 110 form a diverging nozzle leading to the downstream end ofopening 112. The converging nozzles formed by first leading contouredsurfaces 132 and second leading contouredsurfaces 142, and the diverging nozzles formed by first trailing contouredsurfaces 134 and second trailing contouredsurfaces 144 promote the streamlined flow of fuel fromupstream side 102 todownstream side 104 oflast chance screen 100. -
FIG. 2B shows fuel flowing throughopenings 112 with flow arrows F. The fuel that is flowing straight towardsopening 112, represented by the center flow arrow F, will flow straight throughopening 112. The fuel that is flowing towardsfirst members 108 curves inwards aroundfirst members 108 to flow throughopening 112. First leading contouredsurfaces 132 onfirst sides 124 and second leading contouredsurfaces 142 onsecond sides 126 offirst members 108 andsecond members 110 direct the flow of the fuel throughopening 112. First trailing contouredsurfaces 134 onfirst sides 124 and second trailing contouredsurfaces 144 onsecond sides 126 direct the flow of fuel outwards as fuel exitslast chance screen 100 at downstream end oflast chance screen 100. - The airfoil-shaped cross-sections of
first members 108 andsecond members 110 reduces the number of surfaces that are normal to the flow of the fuel compared to prior art last chance screen 50 shown inFIGS. 2A-3B . Rather, first leading contouredsurfaces 132 and second leading contouredsurfaces 142 are tangential to the flow of fuel throughlast chance screen 100. This allows the upstream portions offirst sides 124 andsecond sides 126 offirst members 108 andsecond members 110 to be tangential to the flow of the fuel. This prevents recirculation zones from forming at the upstream surfaces and/or downstream surfaces offirst members 108 andsecond members 110. The contour of first leading contouredsurfaces 132 and second leading contouredsurfaces 142 can be designed to direct the flow of fuel throughopenings 112 throughlast chance screen 100. Further, the contour of first trailing contouredsurfaces 134 and second trailing contoured surfaces 136 can be designed to direct the flow of fuel fromopenings 112 outward into the fuel conduit ondownstream end 104 oflast chance screen 100. - Width W is shown in
FIG. 2B . Width W is the width between firstoutermost edge 130 of a first member and secondoutermost edge 132 of an adjacent member. In a first embodiment, width W is about 0.00394 inches (0.1 millimeter). In alternate embodiments, width W can have any width that is suitable for filtering particles out of the fuel flowing throughlast chance screen 100. Specifically, width W can be selected based on the size of the particles needing filtering out of the fuel and/or the size of the passages and orifices on components downstream oflast chance screen 100. - Half-cone angle A is shown in
FIG. 2B . Half-cone angle A is the angle formed between an end of a member (such as afirst member 108 or second member 110) and a widest point of the member. The widest point of each member is adjacent to a narrowest point of the opening between the member and an adjacent member (located at width W inFIG. 2B ). Half-cone angle A can be between approximately 1 degree and approximately 30 degrees. In the example depicted inFIG. 2B , half-cone angle A is approximately 5 degrees. - As described below in reference to
FIGS. 3-6D ,last chance screen 100 can be formed with a machining process, such as an electrical discharge machining process (which can be supplemented with an abrasive flow machining process).Last chance screen 100 is manufactured to form a monolithic unibody includingfirst members 108 andsecond members 110.Last chance screen 100 can be made out of nickel-based alloys, nickel-chromium-based superalloys, aluminum-based alloys, steel, high strength plastic, nylon, or any other suitable material.Last chance screen 100 can be coated with polytetrafluoroethylene (PTFE). The polytetrafluoroethylene (PTFE) coating is configured to prevent deposits from accumulating on the surface oflast chance screen 100. - The airfoil-shaped cross-section of
first members 108 andsecond members 110 reduces or eliminates coking oflast chance screen 100. The airfoil-shaped cross-section offirst members 108 andsecond members 110 prevent stagnant recirculation zones from forming onupstream end 102 anddownstream end 104 oflast chance screen 100 to help prevent deposits from settling onlast chance screen 100 Eliminating stagnant recirculation zones from forming onupstream end 102 anddownstream end 104 oflast chance screen 100 enables fuel at hotter temperatures, for examples temperatures of greater than 300 degrees Fahrenheit (149 degrees Celsius), to flow throughlast chance screen 100 without coking oflast chance screen 100. This allowsfuel processing system 16 of fuel system 10 (shown inFIG. 1 ) to increase the temperature of the fuel prior to delivering it to fuelnozzles 20 of aircraft engine 12 (shown inFIG. 1 ). This will improve the overall efficiency ofaircraft engine 12, as less energy is needed to combust the fuel in combustor 22 (shown inFIG. 1 ). - Preventing coking of
last chance screen 100 allows fuel to flow throughlast chance screen 100 reduces the pressure drop acrosslast chance screen 100. Reducing the pressure drop acrosslast chance screen 100 reduces the work that fuel pumps infuel system 10 have to do. Further, preventing coking oflast chance screen 100 will extend the life oflast chance screen 100, as deposits will not form on and cloglast chance screen 100. -
FIG. 3 depictsmethod 200 of creating holes (such asholes 302 shown inFIGS. 4B-4D ) in a last chance screen.Method 200 includes steps 202-206.FIG. 4A is a cross-sectional side view ofmetal sheet 300.FIG. 4B is a cross-sectional side view ofmetal sheet 300 afterholes 302 have been formed inmetal sheet 300 with a wire electrode using EDM. Eachhole 302 extends fromfirst end 304 tosecond end 306 and is surrounded bywall sections 308.FIG. 4C is a cross-sectional side view ofmetal sheet 300 afterholes 302 have been shaped by AFM in first direction D1.FIG. 4D is a cross-sectional side view ofmetal sheet 300 afterholes 302 have been shaped by AFM in a second direction D2.FIG. 3 will be discussed with each ofFIGS. 4A-4D in turn below. -
FIG. 4A is a cross-sectional side view, pre-machining, ofmetal sheet 300.Metal sheet 300 can have a uniform thickness of approximately 1/32 inch (0.03125 inches or approximately 0.794 millimeters) and can be a metal alloy such asgrade 304 stainless steel, grade 316L stainless steel, an Inconel® alloy, or another suitable material. - In
step 202,holes 302 are formed inmetal sheet 300 as shown inFIG. 4B . A wire electrode can be used to form uniform through-holes inmetal sheet 300 in a selected pattern. For example, holes 302 can be arranged in a square hole grid (such assquare hole grid 600 shown inFIG. 7A ), a hexagonal hole grid (such ashexagonal hole grid 602 shown inFIG. 7B ), or other suitable repeating or non-repeating patterns. - The wire electrode can form
uniform holes 302 inmetal sheet 300 through electrical discharge machining (EDM). The EDM process removes material frommetal sheet 300 through a rapid series of electrical discharges generated between the wire electrode and the metal sheet (which serves as the other electrode in the system). The wire electrode can be a micro-EDM electrode and can have a constant diameter of between 0.001 inches and 0.25 inches. In some examples, the wire electrode can have a constant diameter of approximately 0.005 inches (approximately 0.127 millimeters). Instep 202,holes 302 can have a width W0 of approximately 0.005 inches. Duringstep 202,metal sheet 300 and the wire electrode do not come into direct contact with each other and can be separated by a dielectric liquid. - In
step 204,first end 304 of eachhole 302 is shaped by a flow of an abrasive flow medium as shown inFIG. 4C . The abrasive flow medium can flow in first direction D1 relative tometal sheet 300. The abrasive flow medium can shape thefirst end 304 of eachhole 302 through abrasive flow machining (AFM). The AFM process removes material frommetal sheet 300 through the use of an abrasive material, such as diamond powder, within the abrasive flow medium. The abrasive flow medium can include a low-viscosity liquid which contains the abrasive. The abrasive flow medium can be directed hydraulically or mechanically throughholes 302 in the first direction at a range of angles in order to achieve a tapered shape of eachhole 302 atfirst end 304. The resulting curvature of the portions ofwall sections 308 adjacent tofirst ends 304 can be convex relative to thecorresponding hole 302. After performingstep 204, eachfirst end 304 can have a width W1 of approximately 0.009 inches. - In
step 206,second end 306 of eachhole 302 is shaped by a flow of the abrasive flow medium as shown inFIG. 4D . The abrasive flow medium can flow in second direction D2 to shape second ends 306. Second direction D2 can be opposite first direction D1 relative tometal sheet 300. The abrasive flow medium can be directed throughholes 302 in the second direction at a range of angles in order to achieve a tapered shape of eachhole 302 betweensecond end 306 andnarrowest point 310. The resulting curvature of the portions ofwall sections 308 adjacent to second ends 306 can be convex relative to thecorresponding hole 302, and can be greater or lesser than the curvature of the portions ofwall sections 308 adjacent tofirst ends 304 depending on the desired dimensions ofholes 302. After performingstep 206, eachsecond end 306 can have a width W2 of approximately 0.009 inches. - Performing steps 202-206 results in airfoil-shaped wall sections (such as
first members 108 andsecond members 110, shown inFIGS. 2A-2B ) and a tapered shape of eachhole 302, with both the first ends 304 and the second ends 306 having a diameter (W1, W2) of approximately 0.009 inches (approximately 0.229 millimeters) andnarrowest point 310 of eachhole 302 having a diameter (W0) of approximately 0.005 inches.Method 200 is a bulk process which allows all first ends 304 or second ends 306 to be shaped uniformly and simultaneously. -
FIG. 5 depictsmethod 400 of creating holes (such asholes 502 shown inFIGS. 6B-6D ) in a last chance screen using shaped EDM electrodes.Method 400 includes steps 402-406.FIG. 6A is a cross-sectional side view ofmetal sheet 500.FIG. 6B is a cross-sectional side view ofmetal sheet 500 afterholes 502 have been formed inmetal sheet 500 by a wire electrode using EDM. Eachhole 502 extends fromfirst end 504 tosecond end 506 and is surrounded bywall sections 508.FIG. 6C is a cross-sectional side view ofmetal sheet 500 afterfirst end 504 of eachhole 502 has been shaped by firstconical sinker electrode 510 using EDM.FIG. 6D is a cross-sectional side view ofmetal sheet 500 after a second end of eachhole 502 has been shaped by secondconical sinker electrode 512 using EDM.FIG. 5 will be discussed with each ofFIGS. 6A-6D in turn below. -
FIG. 6A is a cross-sectional side view, pre-machining, ofmetal sheet 500.Metal sheet 500 can be of the same or a similar thickness as metal sheet 300 (shown inFIGS. 4A-4D ) and can be formed of the same material. - In
step 402,holes 502 are formed inmetal sheet 500 as shown inFIG. 6B using EDM. A wire electrode can be used to form uniform through-holes inmetal sheet 500 in a selected pattern in the same manner, and of the same dimensions, as described above in reference toFIGS. 3 and 4B . Instep 402,holes 502 can have a width W′0 of approximately 0.005 inches. - In
step 404, first ends 504 ofholes 502 are shaped with firstconical sinker electrode 510 using EDM. Firstconical sinker electrode 510 differs from the wire electrode used instep 402 in that firstconical sinker electrode 510 does not create a through-hole inmetal sheet 500. Firstconical sinker electrode 510 can have a conical end and can have a diameter WSE1 of between approximately 0.001 inches and approximately 0.25 inches. In some examples, firstconical sinker electrode 510 can be shaped and operated to create a width W′1 offirst end 504 that is approximately 0.009 inches, thereby wideningfirst end 504 by approximately 0.004 inches. The resulting curvature of the portions ofwall sections 508 adjacent tofirst ends 504 can be convex relative to thecorresponding hole 502. - In
step 406, second ends 506 ofholes 502 are shaped with secondconical sinker electrode 512 using EDM. Secondconical sinker electrode 512 can have a similar shape and similar dimensions (having a diameter WSE2 of between approximately 0.001 inches and approximately 0.25 inches) as firstconical sinker electrode 510 and can operate in the same manner as firstconical sinker electrode 510. In some examples, secondconical sinker electrode 512 can be shaped and operated to create a width W′2 ofsecond end 506 that is approximately 0.009 inches, thereby wideningsecond end 506 by approximately 0.004 inches. The resulting curvature of the portions ofwall sections 508 adjacent to second ends 506 can be convex relative to thecorresponding hole 502, and can be greater or lesser than the curvature of the portions ofwall sections 508 adjacent tofirst ends 504 depending on the desired dimensions ofholes 502. - Performing steps 402-406 results in airfoil-shaped wall sections (such as
first members 108 andsecond members 110, shown inFIGS. 2A-2B ) and a tapered shape of eachhole 502, with both the first ends 504 and the second ends 506 having a diameter (W′1, W′2) of approximately 0.009 inches and anarrowest point 514 of eachhole 502 having a diameter (W′0) of approximately 0.005 inches.Method 400 can be used to shape each end ofholes 502 individually, or can be used as a bulk process with an array of sinker electrodes to shape all ofholes 502 simultaneously (that is, to shape all first ends 504 at once and then to shape all second ends 506 at once). -
FIG. 7A is a top plan view ofsquare hole grid 600 within a last chance screen (such aslast chance screen 100 shown inFIG. 2A ).FIG. 7B is a top plan view ofhexagonal hole grid 602 within a last chance screen (such aslast chance screen 100 shown inFIG. 2A ).FIGS. 7A-7B will be discussed concurrently below.Square hole grid 600 includesholes 604 such thatsquare hole grid 600 forms an array ofholes 604.Hexagonal hole grid 602 includes holes 606 such thathexagonal hole grid 602 forms an array of holes 606. -
Method 200 and/ormethod 400 can be used to create arrays of shaped holes within a last chance screen (such aslast chance screen 100 shown inFIG. 2A ) in a desired pattern. For example, duringstep 202 and/or step 402, the wire electrode can be used to form an array ofholes 604 within the metal sheet (such asmetal sheets FIGS. 4A and 6A respectively) in a pattern that formssquare hole grid 600.Holes 604 are arranged withinsquare hole grid 600 such that eachhole 604 in a particular row and column is aligned with the hole(s) 604 immediately preceding and/or succeeding it in that row and column. Eachhole 604 is thereby surrounded by a square ofholes 604. Alternatively, duringstep 202 and/or step 402, the wire electrode can be used to form an array of holes 606 within the sheet in a pattern that formshexagonal hole grid 602. Holes 606 are arranged withinhexagonal hole grid 602 such that every other row and column ofholes 602 is aligned, and each hole within a particular row and column are centered between the holes of the immediately preceding and/or succeeding row and column. Each hole 606 is thereby surrounded by a hexagon of holes 606. - A method of manufacturing a last chance screen as described above provides numerous advantages. The use of an AFM process allows the entire array of holes to be shaped simultaneously by applying the abrasive flow medium to one side of the sheet. AFM also produces a consistent hole size across the screen without the risk of burrs or other flaws in the screen. Similarly, the use of a conical sinker electrode provides consistent and reliable shaping of the holes in the screen. Finally, machining processes such as EDM and AFM do not require direct contact between a machining tool and the metal sheet, preventing damage or inconsistencies due to tool pressure.
- The following are non-exclusive descriptions of possible embodiments of the present invention.
- A method of manufacturing a last chance screen for an aircraft engine includes forming an array of holes through a metal sheet with a wire electrode using electrical discharge machining. The array of holes comprises a plurality of holes. Each hole of the plurality of holes extends from a first end to a second end. Each hole is surrounded by a wall section such that the last chance screen is defined by the plurality of holes and the plurality of wall sections. The first end of each hole is shaped by applying a flow of an abrasive flow medium to the array of holes in a first direction, such that the first end of each hole is widened by the flow of the abrasive flow medium and a portion of the wall section adjacent to the first end of each hole has a first convex curvature with respect to the hole. The second end of each hole is shaped by applying a flow of the abrasive flow medium to the array of holes in a second direction which is opposite to the first direction, such that the second end of each hole is widened by the flow of the abrasive flow medium and a portion of the wall section adjacent to the second end of each hole has a second convex curvature with respect to the hole. Shaping the first end of each hole and shaping the second end of each hole results in an airfoil-shaped cross-section of each wall section.
- The method of the preceding paragraph can optionally include, additionally and/or alternatively, any one or more of the following features, configurations and/or additional components:
- A method of manufacturing a last chance screen for an aircraft engine according to an exemplary embodiment of the present invention, among other possible things, includes forming an array of holes through a metal sheet with a wire electrode using electrical discharge machining. The array of holes comprises a plurality of holes. Each hole of the plurality of holes extends from a first end to a second end. Each hole is surrounded by a wall section such that the last chance screen is defined by the plurality of holes and the plurality of wall sections. The first end of each hole is shaped by applying a flow of an abrasive flow medium to the array of holes in a first direction, such that the first end of each hole is widened by the flow of the abrasive flow medium and a portion of the wall section adjacent to the first end of each hole has a first convex curvature with respect to the hole. The second end of each hole is shaped by applying a flow of the abrasive flow medium to the array of holes in a second direction which is opposite to the first direction, such that the second end of each hole is widened by the flow of the abrasive flow medium and a portion of the wall section adjacent to the second end of each hole has a second convex curvature with respect to the hole. Shaping the first end of each hole and shaping the second end of each hole results in an airfoil-shaped cross-section of each wall section.
- A further embodiment of the foregoing method, wherein the metal sheet is formed of a stainless steel alloy.
- A further embodiment of any of the foregoing methods, wherein the stainless steel alloy is selected from the group comprising:
grade 304 stainless steel and grade 316L stainless steel. - A further embodiment of any of the foregoing methods, wherein the metal sheet is formed of an Inconel® alloy.
- A further embodiment of any of the foregoing methods, wherein each wall section has a diameter of approximately 0.004 inches at a widest point of the wall section.
- A further embodiment of any of the foregoing methods, wherein each hole has a diameter of approximately 0.005 inches at a narrowest point of the hole.
- A further embodiment of any of the foregoing methods, wherein the plurality of holes are arranged in the metal sheet such that the array of holes forms a square grid.
- A further embodiment of any of the foregoing methods, wherein the plurality of holes are arranged in the metal sheet such that the array of holes forms a hexagonal grid.
- A further embodiment of any of the foregoing methods, wherein the first convex curvature is greater than the second convex curvature.
- A further embodiment of any of the foregoing methods, wherein the second convex curvature is greater than the first convex curvature.
- A further embodiment of any of the foregoing methods, wherein the abrasive flow medium comprises a low-viscosity liquid and a diamond powder abrasive.
- A further embodiment of any of the foregoing methods, wherein the plurality of wall sections comprises a plurality of first members extending in a first direction and a plurality of second members extending in a second direction such that each second member of the plurality of second members intersects at least one first member of the plurality of second members. Each hole is surrounded by two first members and two second members. Each hole forms a square opening at the first end and the second end. Each first member and each second member have an airfoil-shaped cross-section.
- A method of manufacturing a last chance screen for an aircraft engine includes forming an array of holes through a metal sheet with a wire electrode using electrical discharge machining. The array of holes comprises a plurality of holes. Each hole of the plurality of holes extends from a first end to a second end. Each hole is surrounded by a wall section such that the last chance screen is defined by the plurality of holes and the plurality of wall sections. The first end of each hole is shaped with a first conical sinker electrode using electrical discharge machining, such that the first end of each hole is widened by the electrical discharge machining and a portion of the wall section adjacent to the first end of each hole has a first convex curvature with respect to the hole. The second end of each hole is shaped with a second conical sinker electrode using electrical discharge machining, such that the second end of each hole is widened by the electrical discharge machining and a portion of the wall section adjacent to the second end of each hole has a second convex curvature with respect to the hole. Shaping the first end of each hole and shaping the second end of each hole results in an airfoil-shaped cross-section of each wall section.
- The method of the preceding paragraph can optionally include, additionally and/or alternatively, any one or more of the following features, configurations and/or additional components:
- A method of manufacturing a last chance screen for an aircraft engine according to an exemplary embodiment of the present invention, among other possible things, includes forming an array of holes through a metal sheet with a wire electrode using electrical discharge machining. The array of holes comprises a plurality of holes. Each hole of the plurality of holes extends from a first end to a second end. Each hole is surrounded by a wall section such that the last chance screen is defined by the plurality of holes and the plurality of wall sections. The first end of each hole is shaped with a first conical sinker electrode using electrical discharge machining, such that the first end of each hole is widened by the electrical discharge machining and a portion of the wall section adjacent to the first end of each hole has a first convex curvature with respect to the hole. The second end of each hole is shaped with a second conical sinker electrode using electrical discharge machining, such that the second end of each hole is widened by the electrical discharge machining and a portion of the wall section adjacent to the second end of each hole has a second convex curvature with respect to the hole. Shaping the first end of each hole and shaping the second end of each hole results in an airfoil-shaped cross-section of each wall section.
- A further embodiment of the foregoing method, wherein the wire electrode has a constant diameter between 0.001 inches to 0.25 inches.
- A further embodiment of any of the foregoing methods, wherein the wire electrode has a constant diameter of 0.005 inches.
- A further embodiment of any of the foregoing methods, wherein the first conical sinker electrode and the second conical sinker electrode each have a diameter of between 0.001 inches to 0.25 inches.
- A further embodiment of any of the foregoing methods, wherein the first conical sinker electrode widens the first end of each hole by 0.004 inches.
- A further embodiment of any of the foregoing methods, wherein the second conical sinker electrode widens the second end of each hole by 0.004 inches.
- A further embodiment of any of the foregoing methods, wherein a half-cone angle between an end of each wall section and a widest point of each wall section is between 1 degrees to 30 degrees.
- A further embodiment of any of the foregoing methods, wherein the half-cone angle is 5 degrees.
- While the invention has been described with reference to an exemplary embodiment(s), it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment(s) disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.
Claims (20)
1. A method of manufacturing a last chance screen for an aircraft engine, the method comprising:
forming an array of holes through a metal sheet with a wire electrode using electrical discharge machining, wherein:
the array of holes comprises a plurality of holes;
each hole of the plurality of holes extends from a first end to a second end; and
each hole is surrounded by one or more wall sections such that the last chance screen is defined by the plurality of holes and the plurality of wall sections;
shaping the first end of each hole by applying a flow of an abrasive flow medium to the array of holes in a first direction, such that the first end of each hole is widened by the flow of the abrasive flow medium and a portion of the wall section adjacent to the first end of each hole has a first convex curvature with respect to the hole; and
shaping the second end of each hole by applying a flow of the abrasive flow medium to the array of holes in a second direction which is opposite to the first direction, such that the second end of each hole is widened by the flow of the abrasive flow medium and a portion of the wall section adjacent to the second end of each hole has a second convex curvature with respect to the hole;
wherein shaping the first end of each hole and shaping the second end of each hole results in an airfoil-shaped cross-section of each wall section.
2. The method of claim 1 , wherein the metal sheet is formed of a stainless steel alloy.
3. The method of claim 2 , wherein the stainless steel alloy is selected from the group comprising: grade 304 stainless steel and grade 316L stainless steel.
4. The method of claim 1 , wherein the metal sheet is formed of an Inconel® alloy.
5. The method of claim 1 , wherein each wall section has a diameter of approximately 0.004 inches at a widest point of the wall section.
6. The method of claim 1 , wherein each hole has a diameter of approximately 0.005 inches at a narrowest point of the hole.
7. The method of claim 1 , wherein the plurality of holes are arranged in the metal sheet such that the array of holes forms a square grid.
8. The method of claim 1 , wherein the plurality of holes are arranged in the metal sheet such that the array of holes forms a hexagonal grid.
9. The method of claim 1 , wherein the first convex curvature is greater than the second convex curvature.
10. The method of claim 1 , wherein the second convex curvature is greater than the first convex curvature.
11. The method of claim 1 , wherein the abrasive flow medium comprises a low-viscosity liquid and a diamond powder abrasive.
12. The method of claim 1 , wherein the plurality of wall sections comprises:
a plurality of first members extending in a first direction; and
a plurality of second members extending in a second direction such that each second member of the plurality of second members intersects at least one first member of the plurality of second members;
wherein:
each hole is surrounded by two first members and two second members;
each hole forms a square opening at the first end and the second end; and
each first member and each second member have an airfoil-shaped cross-section.
13. A method of manufacturing a last chance screen for an aircraft engine, the method comprising:
forming an array of holes through a metal sheet with a wire electrode using electrical discharge machining, wherein:
the array of holes comprises a plurality of holes;
each hole of the plurality of holes extends from a first end to a second end; and
each hole is surrounded by a wall section such that the last chance screen is defined by the plurality of holes and the plurality of wall sections;
shaping the first end of each hole with a first conical sinker electrode using electrical discharge machining, such that the first end of each hole is widened by the electrical discharge machining and a portion of the wall section adjacent to the first end of each hole has a first convex curvature with respect to the hole; and
shaping the second end of each hole with a second conical sinker electrode using electrical discharge machining, such that the second end of each hole is widened by the electrical discharge machining and a portion of the wall section adjacent to the second end of each hole has a second convex curvature with respect to the hole;
wherein shaping the first end of each hole and shaping the second end of each hole results in an airfoil-shaped cross-section of each wall section.
14. The method of claim 13 , wherein the wire electrode has a constant diameter between 0.001 inches to 0.25 inches.
15. The method of claim 14 , wherein the wire electrode has a constant diameter of 0.005 inches.
16. The method of claim 13 , wherein the first conical sinker electrode and the second conical sinker electrode each have a diameter of between 0.001 inches to 0.25 inches.
17. The method of claim 16 , wherein the first conical sinker electrode widens the first end of each hole by 0.004 inches.
18. The method of claim 16 , wherein the second conical sinker electrode widens the second end of each hole by 0.004 inches.
19. The method of claim 13 , wherein a half-cone angle between an end of each wall section and a widest point of each wall section is between 1 degrees to 30 degrees.
20. The method of claim 19 , wherein the half-cone angle is 5 degrees.
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US17/990,343 US20240167423A1 (en) | 2022-11-18 | 2022-11-18 | Airfoil last chance screen utilizing edm and afm |
EP23210267.3A EP4375006A1 (en) | 2022-11-18 | 2023-11-16 | A method of manufacturing an airfoil last change screen using edm and abrasive flow machining |
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US17/990,343 US20240167423A1 (en) | 2022-11-18 | 2022-11-18 | Airfoil last chance screen utilizing edm and afm |
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US10495002B2 (en) * | 2016-07-14 | 2019-12-03 | Delavan Inc. | Filter screens and methods of making filter screens |
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